This invention relates to a positive displacement pump for moving fluid.
A pump is produced for the purpose of moving fluid. The basic constitution of the positive displacement pump comprises a cylinder, a piston and a pair of check-valves (an admission valve and a delivery valve). Capacity in the cylinder is increased or decreased by reciprocating motion of the piston to vary inner pressure therein, so that the fluid is admitted via the admission valve, compressed and discharged via the delivery valve.
In such a positive displacement pump, the cylinders are normally cylindrical, and fundamentally, pistons corresponding to the cylinders are columnar. Furthermore, the check-valves are normally approximately cylindrical or columnar in their basic constitution.
Accordingly, miniaturization of the pump has to be achieved without demolishing a cylindrical or columnar basic shape, so that the miniaturization is limited. In the number of parts, the pump needs at least four such as the cylinder, the piston and the pair of check-valves as mentioned above.
It is an object of the invention to provide a pump while achieving miniaturization and a decrease in the number of parts.
A pump according to this invention is provided with a cylinder and a piston located inside of the cylinder, wherein the piston is reciprocated and oscillated in the cylinder to take fluid into the cylinder via an intake port formed on the cylinder, to compress it and to discharge it via an outlet port formed on the cylinder.
Thus, the intake port and the outlet port are closed or opened alternately by reciprocating and oscillating motion of the piston; namely, the intake port is opened and the outlet port is closed in a suction process of the piston and the intake port is closed and the outlet port is opened in a discharge process of the piston, so that the fluid can be taken in, compressed and discharged.
Moreover, a center of oscillation of the piston is maintained at a specific position in a long width direction of the cylinder and moved in a depth direction. Thus, opening and closing of the intake port and the outlet port are controlled corresponding to the suction process, the compression process and the discharge process, respectively.
A supporting point for oscillating motion of the piston can be provided by a pair of projecting portions coming in contact with the cylinder.
Reciprocating and oscillating motion of the piston is achieved by circular motion given from the outside to an outer end side of the piston.
Sealing portions for cutting off between a pump chamber and the outside of the cylinder are provided between the piston and the cylinder. The sealing portions may be formed unitedly with or separately from the piston. Thus, leakage of the fluid can be prevented by the sealing portions.
The cylinder is a rectangular parallelepiped shape, and the piston is a shape corresponding and applicable to the shape of the cylinder. Thus, a rectangular parallelepiped thin type pump can be provided.